Filament connection for electric lamp or similar device



EMM

Aug. 23, 1960' F`. .J JAYNE Erm.

FILAMENT CONNECTION ECR ELECTRIC LAMP on slums- DEVICE Filed Hatch 31, 1959 lm/enftos: FTaTwk d. degne, Muvag Honegcuct,

Patented Aug, .23, 1960 PUJAR/DENT CONNECTIGN FOR ELECTRIC LAMP R S DEVICE Frank il. Jayne and Murray Honeycutt, Lyndhurst, Ohio, assignors to General Electric Company, a corporation of New York Filed Mar. 31, 1959, Ser. No. 803,124

Claims. (Cl. 313-471) This invention relates in general to electric incandescent lamps and similar devices and more particularly to an improved joint or connection between the lament and leading-in conductors of such devices.

in the service for which certain types `of incandescent lamps are intended, the lamp is normally subjected to constant or prolonged periods of severe high-frequency vibration. This is particularly true, for instance, in the case of lamps employed for aircraft service such as aircraft marker lamps. Where the laments of such lamps are, for reasons of improved lamp efliciency, unsupported except for their points of connection to the lead-in conductors or wires of the lamp, the resulting iiexure of the filament produced by the vibration of the lamp subjects the ilament connections or joints to severe stresses such as would ordinarily cause the early failure thereof if the lament strength at and adjacent the connection is insufficient. Adequate filament or mount strength against such vibration and resulting stresses therefore becomes an important factor in the construction of such type lamps.

In the case of those incandescent lamps used for such high vibration service and employing laments having coiled end leg portions, the customary practice in forming the connections of the laments to the lead-in conductors heretofore has been to insert a short wire spud or mandrel into the entire length of the coiled end leg portion of the lament for the purpose of, among other things, shorting out the coil turns of the lament end leg so as to keep them from incandescing and thereby establishing the effective or incandescing length of the lilament. The Spud-inserted coiled end leg portions of the filament are then clamped or otherwise secured to the lead-in conductors at points outwardly removed from the main body of the lament.

With such a form of filament connection, because of the relative rigidity or stiffness of the inserted spud, the portion of the coiled filament containing the inserted spud is appreciably less flexible than the adjacent main body portion of the filament. As a result, there is sudden change in the exibility of the filament at that point along its length, outwardly from the main body portion of the filament, where the inserted spud first begins. Consequently, when the filament is subjected to vibration, the stresses produced therein are localized at, and are greatest at the said point of abrupt flexibility change in the iilament, with the result that the iilament soon becomes broken at such point. Accordingly, filament connections such as described are of relatively loW strength and inadequate resistance to withstand stresses such as are customarily imposed on the connection by the vibration normally encountered in aircraft service.

lt is an object of our invention, therefore, to provide an electric incandescent lamp or similar device with a lament joint of greatly improved strength and resistance to vibrational stresses.

Another object of our invention is to provide an electric incandescent lamp or similar device with a ilament joint of a construction such as to produce a gradual decrease in the flexibility of the filament from its main body portion to its point of xed attachment to the lead-in conductor.

Still another object of our invention is to provide an electric incandescent lamp or similar device with a larnent having a coiled end leg joined to a rigid leadin conductor by a connection producing a gradually decreasing iieaibility gradient in the filament from its main body portion outwardly thereof to a point of rigid attachment of the filament end leg to the lead-in conductor, and in addition producing a dampening action on the vibration resonance frequency of the filament.

Briey stated, in accordance with one aspect of our invention, the coiled end legsV of the filament which are rigidly attached to the lead-in conductors of the lamp are provided with inserted wire spuds extending only a minor portion of the length of the coiled end legs inwardly from their point of rigid attachment to the lead-in conductors and in addition are provided with at least one screw-on wire coil in tight screw-mesh engagement therewith and extending a major portion of, and preferably the full length of the coiled end legs inwardly from their point of rigid attachment to the lead-in conductors.

Further objects and advantages of our invention will appear from the following detailed description of species thereof and from the accompanying drawing.

In the drawing,

Fig. l is an elevation, in section, of an electric incandescent lamp having a filament joint comprising our invention.

Fig. 2 is a sectional view, on a greatly enlarged scale, of the filament joint comprising our invention, and

Fig. 3 is' a sectional view, on a greatly enlarged scale,

of a modified form of the lament joint comprising our invention.

Referring to the drawing, the invention is there illustrated as embodied in an electric incandescent lamp of the self-contained reector type such as described and claimed in U.S. Patent 2,148,314, Wright, issued February 21, 1939, and assigned to the assignee of the present invention. The lamp comprises a bulb or envelope 1 consisting of a preformed pressed glass reilector section 2 sealed around its periphery to a preformed press glass cover section 3-. The interior surface of the reector section 2 is of suitable light-concentrating shape such as paraboloidal, for instance, and it is covered with a metallic coating 4, preferably of aluminum, to constitute a reflecting surface. Mounted on the reilector section Z, exteriorly thereof and at the apex of said section, is a base structure 5. The base structure 5 may be of the type described and claimed in U.S. Patent 2,272,512,

Cotman et al., dated February 10, 1942, and comprising a pair of metal lugs 6 suitably secured, as by soldering, to metallic cups or thimbles 7 having their edges sunk and embedded in the glass of the reflector section 2 around openings 8 therein, the cups or thimbles 7 thus hermetically closing the said openings 8. The envelope 1 is exhausted and lled with a suitable inert gas through an exhaust tube 9 attached to the reflector section 2 at its apex. After the gas filling is introduced into the lamp envelope, the exhaust tube 9 is tipped off, as indicated at 10, to hermetically seal the envelope.

Mounted within the envelope 1 and supported therein from the metal thimbles 7 is a mount structure 11 comprising an electric energy translation element orfllament 12 disposed between and connected to a pair of rigid lead-in wires or conductors 13 of suitable material, such as nickel or iron. The lead-in conductors 13 are rigidly secured at their outer ends to the metal thimbles 7, as by soldering or by brazing, and they extend straight through the opening 8 in the reflector section into the interior of, and in more or less parallel relation to one another and preferably in a plane parallel to and including the axis of the reiiector section 2. The lead-in, conductors 13 are held in rigid spaced relation by an insulating bridgeprV cross bar member comprisingra glass i'od 14 extending between and secured to the lead-in conductors 13 by short fastening wires 1S which` may be spot-'welded tothe lead-in conductors. Inwardly of the envelope 1, the lead-in conductors 13 are offset toward ,one yanother to form offset innerend portions 16 to which `the ends of the filament 12 are connected.

or leg portion 18 extending endwise `from the coiled-coil main body portion'17 of the -lament The'said end coil sections 18of vthe lament extend transversely to the respective lead-invconductor portions 16 and are electrically `and mechanically connected thereto by filament joints or connections 19 constructed in accordance with the inventiont To Vthis end, each coiled end leg 18 is provided with a relatively rigid or stili Wire spud insert member 20 and a wire screw-on coil 21, and the assembly of the endcoil 18, insert spud 20 and screw-on coil 21 is rigidly attached to the respective lead-in conductoi" 13 in a suitable manner, preferably by being clamped in hooks 22 formed on the inner ends of the said conductors. 'The wire spud member 20 is composed of a lsuitable .refractory metal such as molybdenum or tungsten, land it is of a wire diameter substantially corresponding to the inside diameter of the coiled end leg 18 of the Ilame'nt so as to more or less 'completely fill the space therein and thus'support .the coil turns againstbecoming crushed during the clamping of the end leg'coil 18 in the hooks 22 such as would ordinarily prevent the formation of a tight 'clamp connection therebetween. The screw-on coil V21 is likewise composed of a suitable refractoryv metal such as molybdenum or tungsten, and it is formed of wire having a diameter preferably at least approximately equal to the wire diameter of the filament 12. The screw-on coil 21 is so constructed as to not only be in screw-mesh engagement with the coil convolutions of the helically coiled filamentend vsection 18, but to also be in denite rictional engagement Ytherewith aswell. To this end, the yscrew-o n coil 21 maybe coiled to an inside diameter corresponding more or less to the pitchv diameter of the filament end coil 18, i.e., to the inside diameter of the filament end coil 18, plus'the Wire diameter thereof, and to a coiling pitch either slightly greater than 'or less than that of the filament end coil 18 so `as to have either one or two less, or `one or two more turns per inch than thev said end coil. By virtue of their snug screw-mesh frictional contactrwith the coil turns of the filament end coils 1,8, the screw-on coils 21 therefore elfectivelyVshort-circuit all those coil turns of the filament endcoils 18 which are in screw-mesh engagement with the respective screw-on coil, Vso that a definite length of Va filament exclusive of the said coil turns of the filament end coils in screw-mesh engagement with the screwon coils is in circuit between the said screw-on coils 21. In accordance with the invention, the distances a and sk (Fig. 2) to which the screw-oncoils 21 and the spuds 20 are screwed onto and inserted into the filament end coils 18 inwardly from the inside edges of the respective lead-in conductors 13 at their points of. clamp connection to .theY filament end coil (such4 points being the first points. along the length of the filament end coils where they Kare fixedly held) `are,soproportioned asV to provide a more or less gradually .decreasing exibility gradient` inthe lament between the-pointsV where the filament endlegs- 18 begin at Ythe, filament proper 17 and the points Where they are clamped within the hooks Z2 4 of the lead-in conductors 13. To this end, the screw-on coils 21 are screw-mesh engaged with the filament end coils `18 for a distance a appreciably greater, for example, from around one and one-half to three times greater, than the distance s of insertion of the spuds 20 into the filament end coils 18. In other words, the spuds 20 extend into thewiilament end coils 18 a distance s ranging lfrom around one-third to two-thirds the distance a of screw-mesh engagement of the screw-on coils 21 with the lament'end coils 18.` Thus, in the preferred form of the inventionrvvlierein the, screw-on coils 21 are in screw-mesh engagement with the entire effective length of the filament end coils 18 extending from their points of clamping in the hooks 22 to their points of junction'with the filament proper 17, the Wire spuds 20 extend only part way into the filament end coils 18 a distance s ranging from about one-half to twothirds the total eiective lengthrof the filament end coils 21 inwardly of their clamped connection within the hooks 22. i f A Because of the progressive stifening action imparted to Vthe filament end coils 18 first by Vthe screw-on coils 21 'which are laterally flexible to a certaindegree, and thence Vby the Spud inserts'Zi which have only a very limited `amount of lateral fiexibility, it will be evidentA that the flexibility of the coiled filament isgradrually decreased from the main body portion 17k thereof to its respective points of rigid attachment or Vclamping to the lead-in con- .ductors y13. "illus, there is Vno abrupt change in the fiexibilityv gradient of the filament 12 toward its respective points ofrigid attachmentror clamping tothe lead-in cond uctors, and vibrational stresses imparted to the filament are effectively distributed throughout the entire length of the filament end coils 18 instead of being localized at one point along their length where they would then cause early rupture ofY Vthe filament wire. The screw-on coils 21 also act to dampen filament vibrations so as to reduce the amplitude thereof and thereby still further decrease the filament rupture-producing effect of such vibrations. The sum result, therefore, of theparticular screwon coil and spud insert construction accordingto the invention is a filament joint 19 of greatly increased strength and resistance to vibrational stresses, and correspondingly increased service life, as compared to that of prior type filament connections involving filaments with helically coiled end leg sections. Thus, actual field tests conducted by commercial air lines on aircraft marker lamps having filament Vjoints constructed according to the in- Vention have shown that the service life or flight hours 'of such lamps is increased to approximately twice that of the prior type lamps providedmerely with wire Vspud inserts in the coiled end legs ofthe filaments. Y Y As a specific representative example of a filament joint 19 constructed in accordance With the invention wherein the filament 12 is constituted'of a helically coiled tungsten Wire having a'wire diameter of approximately 6.19 mils and an inside coil diameter of approximately `13 mils with approximately 83.3 turns per inch, the coiled end legs 18 of the filament and the screw-on coiis 21 extend a distance a Aof approximately 1.8 mm. from the inside edge of the lead-in conductor hooks v22 While the insert spuds 20 extend a distance s of approximately Y1 mm. inwardly of the filament end coilsY 1S from the inside edge of the lead-.in conductor hooks 22. The screwon coils 21 are constituted of helically coiled molybdenum wire having a wire diameter of approximately 6.719 mils and an inside coil diameter of approximately 18mils with approximately 81.3 turns per inch.V Thewire insert spuds 29V are constituted of molybdenum wire having a wire diameter of `approximately 12 mils, Y l

Fig. 3 illustrates a modied form-of filament joint 23 accordingto the invention wherein a second screw-on coil .24 is screwed 'over the rrst or primary screw-on coil 21. As shown, the secondary screw-on coil 24 is screwn'ieshed ,with the primary screw-on coil 21 a distance assente b which is intermediate, and preferably approximately half way between the distances a and s that the primary screw-on coil 21 and the insert spud 20 are screw-meshed with and extend into the filament end coils 18 from the inner sides of the respective lead-in conductor hooks 22. The secondary screw-on coils 24 exert an additional stiffening effect on the filament end coils 18 vat regions intermediate the inner ends of the primary screw-on coils 21 and the relatively rigid spuds 20, which additional stiffening eiect is intermediate in degree to that imparted to the filament end coils by the primary screw-on coils 21 and the wire spud inserts 20. As a result, a more gradual change in the flexibility of the filament toward its points of rigid attachment to the lead-in conductors is aorded by the multiple screwon coil arrangement of Fig. 3, as compared to the single screw-on coil arrangement of Fig. 2, and a more uniform flexibility gradient is imparted to the filament, thus further increasing the resistance of the iilament to rupture by vibrational stresses.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. In an electric lamp, the combination of a lead-in conductor, a filament comprising a main body portion having a helical end coil portion, a wire Spud extending into and in contact with said end coil, and a wire screwon coil tightly screwed over an appreciable portion of the length of said end coil and short-circuiting the coil turns thereof, the coil-enclosed Spud-containing portion of said lament end coil being fixedly attached to said conductor at a point removed from the said main body portion of the iilament, said wire spud extending into and engaged with said iilament end coil a distance, inwardly from its said point of xed attachment to the conductor, ranging from approximately one-third to two-thirds the distance of screw-mesh engagement of said screw-on coil with said iilament end coil inwardly thereof from its said point of fixed attachment to the conductor.

2. In an electric lamp, the combination of a lead-in conductor, a iilament comprising a main body portion having a helical end coil portion, a wire spud extending into and in contact with said end coil, and a wire screwon coil tightly screwed over said end coil and shortcircuiting the coil turns thereof, the coil-enclosed spudcontaining portion of said filament end coil being fixedly attached to said conductor at a point removed from the said main body portion of the iilament, said screw-on coil being in screw-mesh engagement with substantially the entire length of said lament end coil inwardly thereof from its said point of fixed attachment to the conductor and said wire spud extending only part way into said filament end coil inwardly from its said point of iixed attachment to the conductor.

3. In an electric lamp, fthe combination of a lead-in conductor, a filament comprising a main body portion having a helical end coil portion, a wire Spud extending into and in contact with said end coil, and a wire screwon coil tightly screwed over said end coil and shortcircuting the coil turns thereof, the coil-enclosed spudcontaining portion of said filament end coil being ixedly attached to said conductor at a point removed from the said main body portion of the iilament, said screw-on coil being in screw-mesh engagement with an appreciable portion of the length of said filament end coil inwardly thereof from its said point of xed attachment to the conductor yand said wire spud extending into said filament end coil only a minor part of its length inwardly from its said point of fixed attachment to the conductor.

4. In an eiectric lamp, the combination of a lead-in conductor, a filament comprising a coiled-coil main body portion having a helical end coil portion, a wire spud extending into and in contact with said end coil, and a wire screw-on coil tightly screwed over said end coil and short-circuiting the coil turns thereof, the coil-enclosed Spud-containing portion of said end coil being tightly clamped to said conductor at a point removed from the said main body portion of the filament, said screw-on coil being in screw-mesh engagement with substantially the entire length of said filament end coil inwardly thereof from its said points of clamped connection to the conductor and said wire spud extending into said iilament coil a distance, 'inwardly from its said point of clamped connection to the conductor, ranging from approximately one-third to two-thirds the said entire length of the filament end coil inwardly of its said clamped connection to the conductor.

5. In an electric lamp, the combination of a lead-in conductor, a lament comprising a main body portion having a helical end coil portion, a wire spud extending into and in contact with said endcoil, a primary wire screw-on coil tightly screwed over said end coil and short-circuiting the coil turns thereof, and a secondary wire screw-on coil tightly screwed over said primary screw-on coil, the coil-enclosed Spud-containing portion of said end coil being iixedly attached to said conductor at a point removed from the said main body portion of the filament, said primary screw-on coil being in screwmesh engagement with substantially the entire length of said iilament end coil inwardly thereof from its said point of fixed attachment to the conductor, said wire spud extending into said filament end coil only a minor part of its length inwardly from its said point of xed attachment to the conductor, and said secondary screw-on coil being in screw-mesh engagement with said primary screwon coil a distance, inwardly thereof from its said point of r'ixed attachment to the conductor, intermediate the distance of screw-mesh engagement of said primary screwon coil with the iilament end coil and the distance of insertion of said wire Spud into the filament end coil, inwardly thereof from its said point of xed attachment to the conductor.

References Cited in the le of this patent UNITED STATES PATENTS 2,084,999 Birdseye June 29, 1937 2,134,574 Pinkle Oct. 25, 1938 2,404,992 Stone July 30, 1946 2,449,679 Van Horn Sept. 21, 1948 

